The tiny
pebbles were collected by astronauts during NASA’s Apollo missions of the 1970s,
but the techniques used to find the traces of water weren’t available until
recently.

The report’s
authors conjecture that small volcanic eruptions more than three billion years
ago released most of the moon’s water into space, while some was trapped in the
volcanic pebbles. Water could still be trapped in the rocks at the moon’s
poles, which could affect future NASA explorations, the researchers said.

Someday, astronauts
establishing a permanent base on the moon might — depending on the extent of
the water — be able to extract it for drinking purposes or create hydrogen to use
as fuel, Saal told ABC News.

“Could
a colony use the water? That’s like asking the final score of a football game
in the first five minutes of the first quarter,” Saal said. “But at
least we know there’s a game on.”

One goal of NASA’s
Lunar Reconnaissance Orbiter mission, due to launch later this year, is to
verify the presence of ice on the moon. That’s also an objective of the Lunar
Crater Observation and Sensing Satellite, which is set to launch next year.

Researchers
have seen hints of ice near the moon’s poles before, but previously thought
that any ice on the moon would have had to have come from a meteorite impact.
The new finding suggests that it’s possible that some of that ice might come
from the moon itself.

“There
is a chance that there might be some very old water of the type that they
discuss in the paper,” Ben Bussey, of the Johns Hopkins University Applied
Physics Lab, told National Public Radio.

The finding
also raises new questions about the “giant impact” theory of how the
moon was formed. That theory says that a Mars-sized planetary body hit the
Earth 4.5 billion years ago. Rocky debris darted out into space, some of which orbited
around the Earth and amassed into the moon.

But that
theory is hard to reconcile with the presence of water, because scientists
believe that the heat of the impact would have vaporized any water.

“It’s
hard to imagine a scenario in which a giant impact melts, completely, the moon,
and at the same time allows it to hold onto its water,” Erik Hauri, a
geochemist at the Carnegie Institution’s Department of Terrestrial Magnetism in
Washington, D.C., told NPR. “That’s a really, really difficult knot to
untie.”

The search
for evidence of water on the moon had until now eluded all efforts, and Saal
and his colleagues were denied funding for this study for three years.

Once
they received the funding, they used a new and extremely sensitive technique
for analyzing the rocks, which were collected during the Apollo 15 mission in
1971 and the last visit by Apollo 17 in 1972.

The
high-powered imaging technique, known as secondary ion mass spectrometry,
revealed compounds of fluorine, chlorine, sulfur, carbon dioxide and traces of
water’s constituents, such as hydrogen. The beads contained up to 46 parts per
million of water.

Hydrogen
molecules were concentrated at the center of the tiny glass pebbles, which
points to the presence of water in an infant moon. The researchers estimate
that the interior of the moon once probably contained an amount of water equal
to that of the Caribbean Sea.

Since
the rocks were brought back to Earth, they’ve been kept in nitrogen gas at the
Johnson Space Center in Houston, Texas, according to The Guardian.

This summer,
Saal’s team is continuing to look for water in volcanic glasses gathered from
other Apollo missions to
determine how widespread the water might be.

“It is
remarkable that people are going back to rocks that we’ve had lying around for
decades and figure out things like what they’ve done,” David Stevenson, a
planetary scientist at the California Institute of Technology, said to National
Geographic. “That’s impressive.”

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